A typical Universal Mobile Telecommunication System (UMTS) in accordance with current Third Generation Partnership Project (3GPP) specifications is depicted in FIG. 1. The UMTS includes a Core Network (CN) interconnected with a UMTS Terrestrial Radio Access Network (UTRAN) via an Iu interface. The UTRAN is configured to provide wireless communication services to users having wireless transmit receive units (WTRUs) via a Uu interface. The UTRAN has one or more Radio Network Controllers (RNCs) and Node-Bs, which collectively service the geographic coverage of the wireless communication system for WTRUs.
One or more Node-Bs are connected to an RNC via an Iub interface. The UTRAN may have several groups of Node-Bs connected to different RNCs. Where more than one RNC is provided in a UTRAN, inter-RNC communication is performed via an Iur interface.
In a 3GPP communication system, multiple shared and dedicated channels of variable data rates are combined for transmission. Transport Channels (TrCHs) are used for transfer of user data and signaling between WTRUs and a Node-B or other devices within the communication network. TrCHs are a composite of one or more physical channels defined by mutually exclusive physical resources. TrCH data is transferred in sequential groups of Transport Blocks (TBs) defined as Transport Block Sets (TBSs). Each TBS is transmitted in a given Transmission Time Interval (TTI). For each TrCH, a Transport Format Set (TFS) is specified. Each Transport Format (TF) defines a TBS comprising a specified number of TBs, where each TB preferably has the same size within a given TBS.
The Radio Link Control (RLC) function generates octet-aligned PDUs (i.e., 8 bit quantities). Thus, the RLC PDUs are defined as groups of selected number of octets, such that the RLC PDU bit size is always evenly divided by eight. All data transferred by specific TrCHs must fit into the TB sizes specified for the TFS of a particular TrCH. However, variable size data blocks exist that cannot be predicted for Random Access Network (RAN) and CN signaling data as well as Non-Real Time (NRT) user data transmissions.
In order to allow for the transfer of variable size data blocks, the RLC provides a segmentation and reassembly function and a padding function. The segmentation and reassembly function reduces the size of data blocks and is used when a data block is larger than the maximum allowed TB size. The padding function increases the data block or segmented data block size by padding it with extra bits to fit a specified TB size.
Each RLC PDU can contain one or more unrelated data blocks, or a portion of a data block. The final internal composition of the RLC PDU is not determined until transmission of the RLC PDU is requested. Therefore, it is inefficient to build part of the RLC PDU and have to rebuild it later, when additional data blocks are added to the RLC PDU.
FIGS. 2(a) and 2(b) illustrate RLC PDUs for transmitting data blocks under current 3GPP specifications for an unacknowledged mode (UM) and on acknowledged mode (AM), respectively. At the front of the PDU are a series of length indicators (LIs). The LIs indicate the last octet of data blocks ending within the PDU. Following all the LIs are blocks of data to be transmitted.
Information relating to each separate block of data is conveyed along with, but separated from, the data blocks which are grouped together in the PDU. Data blocks are sequentially assembled as they become designated for a particular transmission unit. Conventionally, each data block of the PDU is written into a memory individually as it became designated for inclusion in a PDU.
Prior art systems need a significant amount of time for rearranging the data blocks within the formatted PDU. In order to add another data block and its corresponding LI, the previous data block must be moved over by one or two bytes in order to add a new LI after the previous one. As each data block is added, the amount of data that needs to be shifted to accommodate new LIs gets larger and larger. This incurs a tremendous number of processing cycles and, therefore, time.
Accordingly, it is desirable to provide a more efficient processing method and apparatus for assembling unrelated data blocks into a PDU for transmission.